The present invention relates to chromatography columns and in particular to a chromatography column system and method of compressing and maintaining optimal or a consistent compression on a media bed within a chromatography column. Frequently it is desirable to separate out one or more useful components from a fluid mixture that contains other components that may not be useful or are less valuable. To accomplish this, it is often necessary or desirable to fractionate such a fluid mixture to separate out the useful or desired components. This can be carried out by using liquid chromatography systems. Liquid chromatography may be described as the fractionation of components of a mixture based on differences in the physical or chemical characteristics of the components. The various liquid chromatographic systems fractionate the components with a fractionation matrix. Some liquid chromatographic matrix systems fractionate the components of a mixture based upon such physical parameters as molecular weight. Still other liquid chromatographic systems will fractionate the components of a mixture based upon such chemical criteria as ionic charge, hydrophobicity, and the presence of certain chemical moieties such as antigenic determinants or lectin-binding sites on the components.
Chromatography systems of various sizes are used in both laboratory analysis operations and for industrial scale production operations in which separation steps such as separating out a fraction from human blood or separating out impurities from a pharmaceutical can be carried out on a large scale in a batch process.
Separations using chromatography columns filled with chromatographic media have been carried out for years. The chromatographic media typically comprises particles having a diameter between 5 and 100 μm. To maximize the effectiveness of the column, it is desirous to arrange the media as tightly and as uniformly as possible. This process, known as packing, eliminates voids and channels within the media. However, chromatography column packing, particularly where large columns are involved, is highly variable and can dramatically affect the efficiency of the separation. Many setup process parameters must be smoothly orchestrated in order to achieve a homogenous packed column. Depending on the size of the column, the packing process can take a significant amount of time, in the range of several hours. Yet despite the time invested in packing the column, often times less than 50% of these packed columns function in accordance with the specification.
During chromatography packing and operation, the compaction of the chromatographic media has a significant impact on the performance and repeatability of the column. In packing the column, typically the media is compressed through an alternating process of flowing liquid through the column to pack the media and then lowering the adjuster assembly in an effort to mechanically compress the media.
Once the column has been packed, the fluid to be fractionated is then passed through the column. During extended operation, packed media beds will experience a variety of issues with the media.
In some media, as it is wet with the packing and/or process fluid, it swells. This can cause an overcompression of the media potentially damaging the media or leading to a decrease in separation efficiency due to a reduction in the media pore sizes or availability of the media to the process stream.
Also a slight, but noticeable and cumulative bed compaction occurs. This is intrinsic to many packed bed columns. The sources of this further compaction are principally process-dependent and are generally due to the hydraulic drag of processing, flow perturbations during process cycles, mobile phase properties, such as flow rate, viscosity and density, support matrix swelling, and the intrinsic bead mobility in the packed bed superstructure. The magnitude of the compaction is also related to the size, shape and rigidity of the medium particles. For example, irregularly shaped particles such as PROSEP® matrix will be predisposed to de-bridging and the accompanying compaction.
The long-term result is that as a packed bed is repeatedly used, it incrementally compacts. This compaction leads to a continuous reduction in media bed density at the top of the bed, until a breach forms between the bed and the top bed support. The immediate performance implications are a decrease in separation efficiency, typically characterized by broader elution peaks with more tailing. Ultimately, this reduced bed density can lead to the formation of preferential flow channels through the bed, decreasing the effective life of the column, thereby necessitating more frequent repacking.
Therefore, there is a need for an improved method of maintaining proper compression within a packed chromatography column during operation, which will improve the performance of the column and extend its useful life.